A projection device is a common image display device and has been extensively utilized for living entertainments, academic presentations, and business demonstrations. According to the principles of display, projection devices can be categorized into cathode-ray tube (CRT), liquid crystal display (LCD), digital light processing (DLP), and liquid crystal on silicon (LCoS) based projection devices.
DLP projectors modulate light beams emitted from its light source by a digital micro-mirror device (DMD). DLP projector projects images onto a projection screen via an optical projection system. Single or dual light valves of the projector utilizes wheel assembly to filter some colors from the light source and thus display another colors. Preferably, the wheel assembly is designed to project images with wide color gamut, high brightness, and ideal white balance.
A standard wheel assembly is comprised of phosphor powder in the surface of the wheel. The area of light exposure of the phosphor powder coated on the wheel would increase with rotation of the wheel. However, dust particles may adhere to the phosphor powder during wheel rotation, causing reduction in optical efficiency of the phosphor powder. Consequently, most wheel assemblies are disposed inside of an enclosed housing to prevent dusts. However, excessive thermal energies would be generated from energy loss occurred during light conversion and from the motor driving the wheel to rotate, thus causing elevated temperature inside of the housing and reduced optical efficiency due to overheated phosphor powder. Meanwhile, adhesives for coating the phosphor powder are generally weakly resistant to heat; therefore, the adhesives may potentially be burned when the housing is overheated from the inside.
The information disclosed in this “BACKGROUND OF THE INVENTION” section is only for enhancement understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Furthermore, the information disclosed in this “BACKGROUND OF THE INVENTION” section does not mean that one or more problems to be solved by one or more embodiments of the invention was acknowledged by a person of ordinary skill in the art.